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Best swale depth with raised beds?

Sean Flynn

Joined: Apr 30, 2012
Posts: 1
Location: Calgary
Hi there. I've been lurking for a while but finally have a question that I can't seem to find answered already.

I have raised beds in my suburban yard planted mostly with vegetables. I want to take the water from my downspouts/water barrel overflows and run them to a swale that goes around the raised beds. I'm not sure if it is a swale or a wicking bed or what exactly it would be called. But the plan is this water would then be able to provide for most (all? some? a bit?) of the water needs of the vegetables. I plan to fill the swale with wood chips/straw/leaves to give me a pathway to access the beds. The yard around the beds is pretty darn close to flat. I'm sure there is a slight slope I'll find as I start digging but to the naked eye it looks flat. The soil surface in the raised beds is around 8-10" above ground level. I was thinking of a swale around a foot deep and two feet wide (or so - path width) but after finding the info on wicking beds I am second guessing myself. For wicking beds, they talk about 300cm/12" as being the maximum water will come up a lot. For swales, it seems to generally be more of a function of how much water you need to retain and I haven't found much about how far up the water will come.

What do you guys figure would be a good depth for my swale so that it would still be of a benefit to a raised bed? I don't want the water so deep it can't percolate up into the raised beds at all.

Morgan Morrigan

Joined: Oct 16, 2011
Posts: 1400
Location: Verde Valley, AZ.
You can use a laser pointer and a level to figure out which way the land slopes pretty easy, just tape it on top. You may need to use a longer pipe or piece of wood to get a true reading.

Going to be hard to get it to wick up from exterior. Wicking beds pull up from directly below, that is how we are building our hegels out west, basically wood filled pits.
Swales would just be to direct the water and let it seep in, as you said.

Best bet is to dig around the outside base of the planters, put in pea gravel, and just a thin layer of mulch. i would put some boric acid on the gravel myself.
if just wood chips, you are going to bring in and harbor lots of pests, and i know of no good bugs that live in deep mulch......

you would just be keeping the lower soil moisture there, wouldnt help much but the deep rooted stuff, but will cut down on the raised beds dehydrating.

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John Polk

Joined: Feb 20, 2011
Posts: 6877
Location: Currently in Seattle. Probably moving 1 hour north by end of the year.
I agree that the water should go directly into the bed itself.

Otherwise, you are likely to have soggy paths and dry beds. Very little water will work its way sideways and up.
If your bed soil has better tilth than the soil in the paths (hopefully!), water put directly into the beds will disperse throughout the beds. Most water put into swales in the pathways will just go down, forcing your roots to try to grow into compacted paths to find water.

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